1. Field of the Invention
The present invention relates to a network device, network system and method for enabling service support according to quality of service (hereinafter referred to as “QoS”). More specifically, the present invention relates to a network device, network system and method for enabling service support according to QoS, wherein priority for service is assigned according to the QoS for a control point and appropriate services are provided according to the assigned priority.
2. Description of the Related Art
FIG. 1 is a diagram schematically illustrating the configuration of a related Universal Plug and Play (UPnP) system which comprises a UPnP control point 20 and a UPnP control device 10.
The UPnP control point 20 is configured to control the control device 10 and may correspond to, for example, a digital TV 21, a personal computer 22, a PDA (Personal Digital Assistant) 24, a notebook computer 23, or the like.
The UPnP control device 10 provides services using UPnP and may correspond to, for example, a set-top box for playing back and transmitting motion pictures over a network. The UPnP control device 10 comprises a communication software (S/W) module 11, a UPnP S/W module 12 and a service SW module 13.
The communication S/W module 11 functions to receive request data transmitted over a network from the UPnP control point 20 or to transmit reply data to the UPnP control point 20. The UPnP S/W module 12 analyzes the request data to activate the service S/W module 13 or creates reply data and transfers the created reply data to the communication S/W module 11. Further, the UPnP SW module 12 functions to transmit an event message to the UPnP control point 20 when the state of the control device 10 is changed. In addition, the service SW module 13 corresponds to software for providing inherent functions of the control device 10, and decrypts motion pictures to produce picture images in the case of a set-top box, for example.
The operation of the UPnP system will be now described. When control data are transmitted from the UPnP control point 20, the communication S/W module 11 receives the control data. Since Transmission Control Protocol (TCP) is generally employed for data communications in the UPnP system, the communication S/W module 11 includes a TCP connection function.
The received data are transferred to the UPnP S/W module 12. Here, since commands and response data are in Extensible Markup Language (XML) format, the UPnP S/W module 12 analyzes the XML data to activate the requested service via the service S/W module 13.
Then, when the service is provided, the UPnP S/W module 12 generates the result of the service in XML format and transmits the created result to the UPnP control point 20.
That is, the UPnP system processes the tasks requiring intensive computation such as XML analysis, TCP connection, HTTP handling and Java, and also performs a variety of incidental functions of notifying the presence of the UPnP control device 10, checking a change of state of the UPnP control device 10 and the like, in addition to the function of controlling the UPnP control device 10 directly related to the service.
However, each of the UPnP control devices 10 of a home network generally includes a CPU with relatively lower performance than general-purpose computing platforms such as PCs. Thus, the operational overhead of the UPnP system is increased as the number of UPnP-enabled control points 20 is increased.
For example, if a digital TV 21 for receiving motion pictures from a set-top box and outputting them to a screen is further provided, the image output from the digital TV 21 can be subject to interference due to the control commands transmitted from other associated output devices such as a PC 22, a notebook computer 23 and a PDA 24. In the worst case, there is a problem in that the satisfaction level of a user may be decreased due to intermittent display, increased control time and the like.
Therefore, to prevent inconvenience to the user due to contentions between a plurality of UPnP control points 20, there is a need for a network system and method for enabling service support according to quality of service (QoS) wherein a predetermined QoS level is assigned to each of the UPnP control points 20 and priority according to the QoS is assigned to the UPnP control device 10.